| Hydraulic transmission is widely used on various types of vehicles.However,due to the existence of torque converter,although the range of torque is increased,and the vehicle has load adaptability,the transmission efficiency is lower than the mechanical transmission.In order to improve the transmission efficiency of the system,adding a lockup clutch between pump and the turbine of the torque converter.According to the needs of different working conditions,control the separation and combination of lockup clutch.Complete mechanical and hydraulic transmission switching.Thus,the transmission efficiency and reliability are effectively improved.This paper takes the power transmission system of a wheel loader as the research object.In order to reduce the occurrence of resonance phenomenon when loaders work,and reduce the impact of hydraulic and mechanical switching.Conduct the following study:The equivalent mechanical model of loader transmission system is established.Calculate the inherent characteristics of the torsional vibration.Determine the critical speed and resonance frequency of the engine which lead to the resonance phenomenon happens.Through the calculation and analysis of the installation position and torsional rigidity of the torsional damper,complete the matching of the transmission system and the torsional vibration damper.To achieve the purpose of reduce the occurrence of resonance.The transmission system after matching is considered as the research object.Simulate the process of locking and unlocking before and after connecting the torsional vibration damper.The results show that the use of torsional dampers can improve the lock quality.Based on the throttle of the engine and the turbine speed of the torque converter,consider the release of inertial energy from the engine,to optimize the traditional law of locking.Based on the analysis of the causes of the locking-unlocking cycle,the dual parameter convergence type locking and unlocking rules are designed.Simulate locking laws before and after optimization,the results show: locking at the optimized locking point,the friction time,friction work and impact are reduced compared with the traditional locking point.The locking quality has been greatly improved.Considering the effects of friction time,friction work and impact on the lock quality,according to the idea of multi-objective optimization,construct a locking quality assessment function.Using the method of experimental design,the buffer slope of the buffer boost phase in the oil-filled characteristics is an optimization variable.An optimization model based on the slope of the buffer is established.Obtain the lockup oil-filling characteristics that make the lock quality best.For the optimized buffering law,design and build test benches consisting of engine,torque converter,dynamometer,pump station,etc.The test of the dynamic process of locking is carried out.The results showed that: the optimized locking buffering law can significantly improve the lock quality,the impact is significantly reduced. |
